DESCRIPTION: The investigators propose to test the feasibility of developing algorithms and software for conversion of bone mineral measurement data from X-ray computed tomography to a projection format comparable to a dual-energy X-ray absorptiometry device, as further described by their abstract: "QCT and DXA are clinically used methods for measurement of bone density in the central skeleton. DXA is considered to be the method of choice by the internal medicine community, but the number of centers worldwide doing DXA is not sufficient to make this technique generally available. There is an order of magnitude larger number of CT scanners. "3DQCT improves the precision of QCT by eliminating repositioning errors in serial exams. A volumetric data set is acquired and transferred to a PC for analysis. Clinically, 3DQCT is used for spinal bone mineral density (BMD) analysis, but also in research studies for regional BMD in the proximal femur. Segmentation algorithms used in CT separate bone from soft tissue or contrast-filled vessels from tissue, and the resulting data are projected into a 2D image for visualization. We will apply these methods to 3DQCT to construct pseudo-DXA images for BMD analysis. The key factor is the ability to measure BMD accurately voxel-by-voxel in the 3DQCT data set. "The long-term objective of this proposal is to show that 3DQCT can substitute for DXA, while at the same time using the vast set of clinical knowledge developed using DXA. If successful, this work can make DXA-like BMD results available to any site with a CT scanner." PROPOSED COMMERCIAL APPLICATION: Proposed commercial application not available.